Now works with memcacheD

Problem as mentioned here (http://forrst.com/posts/Looks_like_I_was_a_bit_too_eager_to_get_code_out-9h5#comment-land) could not be reproduced.

Setup

MY_Session.php -> application/libraries
memcached.php -> application/config
Fixed instant expiration of items

Memcached servers uses unix timestamp when the TTL is above 30 days. If
you specify 2 years for sess_expiration, it takes Unix time (1972).
Fixed adding current timestamp.
Merge branch 'master' of git://github.com/dennisvdvliet/codeigniter-session-memcached
Fixed session expiration after sess_time_to_update

The bug occurred when updating the session. It was because it was saved
in a way different from that which was saved at the time of the creation
of the session.  Therefore, the sessions were lost past 300 seconds
(default sess_time_to_update)
Updated readme

Its working pretty well on my production server.
Merge pull request #2 from killgt/master

Bug fix on sess_expiration = 0